Reciprocity is when an infant and a mother respond to each others signals.
Interactional synchrony is when an infant and a carer mirror each other's behaviours.
Isabella et al. observed 30 mothers and babies together and assessed the degree of synchrony and the quality of attachment.
->She found that high levels of synchrony were associated with higher-quality attachment.
Limitation) Its hard to observe baby behaviour because they are not very coordinated which means that its hard to interpret he meaning of babies behaviour. e.g. a baby moving their hand in response to their mother may just be a random twitch.
Strength) Research done on mother-baby interactions are often filmed, from multiple angles which allows for detailed analysis of behaviour. Also because the babies don't realise they are being observed, their behaviour doesn't change.